Recently, so-called social network games have become widespread which run on game applications created on the basis of operating environments such as application programming interfaces (API) operated on a web browser in a social networking service (SNS) provided by a particular service provider. Social network games may be defined as a type of online game played among a plurality of unspecified users who are communicating with each other. A user who has a communication terminal connectable to the Internet and with a web browser installed is able to enjoy social network games regardless of time or location.
One characteristic of the abovementioned social network game is that communication functions for socializing between users are more sophisticated than those of conventional online games. For example, in social network games, besides collaborative play with other users (friends), users exchange information through communication with friends such as greetings and contacts, and give or exchange items in the game with friends. In the digital card game (Dragon collection (registered trademark)) disclosed in a Japanese game magazine (Appli Style, Vol. 2 (Eastpress Co., Ltd.) p. 26-27.), items are distributed to respective users based on a number of login users.